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MAX Administration Guide
Administering TCP/IP
Managing the Open Shortest Path First (OSPF) protocol
Third-party routing
A MAX running OSPF can advertise routes to external destinations on behalf of another
gateway (a third party). This is commonly known as advertising a forwarding address.
Depending on the exact topology of the network, other routers might be able to use this type of
link-state advertisement (LSA) and route directly to the forwarding address without involving
the advertising MAX, thereby increasing the total network throughput.
Third-party routing requires that all OSPF routers know how to route to the forwarding
address. This usually means that either the forwarding address must be on an Ethernet that has
an OSPF router acting as the forwarding router or the designated router is sending LSAs for
that Ethernet to any area that sees the static route’s forwarding-address LSAs. The following
example shows how to configure a static route for OSPF to advertise a third-party gateway:
1
Open a static route in Ethernet > Static Rtes.
2
Set the Gateway to the forwarding address and set Third-Party to
Yes
.
Ethernet
Static Rtes
40-401
SRprofile1
Name=SRprofile1
Active=Yes
Dest=10.212.65.0/24
Gateway=101.2.3.4
Metric=3
Preference=100
Private=No
3
Close the static route.
How OSPF adds RIP routes
When the MAX establishes an IP routing connection with a caller that does not support OSPF,
it imports the AS-external route from the Connection profile and adds it to the routing table.
The MAX does not have to run RIP to learn these routes. In fact, RIP should be turned off
when the MAX is running OSPF.
To enable OSPF to add the RIP-v2 routes to its routing table, configure RIP-v2 normally in the
Connection profile. OSPF will import all RIP routes as Type-2 Autonomous System Externals
(ASEs). The reason that RIP routes are imported with Type-2 metrics by default is that RIP
metrics are not directly comparable to OSPF metrics. To prevent OSPF from interpreting RIP
metrics, the imported ASE route is assigned a Type-2 metric, which is so large compared to
OSPF costs that the metric can be ignored.
Route preferences
Route preferences provide additional control over which types of routes take precedence over
others. They are necessary in a router that supports multiple routing protocols, largely because
RIP metrics are not comparable with OSPF metrics.
For each IP address and subnet mask pair, the routing table holds one route per protocol. The
routes are assigned preferences as follows: